• homozygotes are resistant to experimental Lyme disease regardless of the inoculation mode (needle inoculation versus tick transmission of spirochetes); similar effects between the infection dose and tissue colonization by Borrelia burgdorferi are observed by either inoculation procedure
• at low infection doses, most mutant tissues have fewer Borrelia-positive blood cultures relative to wild-type; these differences are generally eliminated at high infection doses
• notably, joints from mutant mice have fewer Borrelia-positive cultures and reduced Borrelia numbers regardless of infection dose; also, mutant joints are found to be less arthritic, regardless of the genetic background of mice
• no differences in Borrelia-positive cultures are generally noted in skin biopsies regardless of genotype or infection dose, although homozygotes have fewer Borrelia-positive skin biopsies than wild-type mice when low-dose tick transmission is used
• homozygotes (BALB/c) are at least as susceptible as wild-type mice to S. aureus-induced septic arthritis (unpublished), arguing against an enhanced host defense against bacterial infections